1. Field of the Invention
The present invention relates to a method and apparatus for controlling a centrifugal thin film dryer.
2. Description of the Prior Art
The centrifugal thin film dryer dehydrates slurry (i.e., drainage or refuse such as sullage emanating from industrial waste streams and sewage, having a composition of liquid and solid mater which may vary as a function of time) for separating solid matter and moisture, and because bringing an effective method of dehydration and allowing easy handling of solid matter which is obtained in powder form, it is widely used in processing systems for waste fluid and the like.
The centrifugal thin film dryer has been controlled by the method described in Japanese Patent Publication No. 33559/80. In this method, a plurality of thermal sensors are provided in the drying region and evaporating region within the centrifugal thin film dryer and the flow rate of slurry to be fed to the dryer is controlled in accordance with the temperature signals provided by the sensors such that each section of the dryer has a specified temperature.
In this method, however, the degree of dryness of sullage within the dryer cannot be known accurately as will be mentioned later, and accordingly, controlling of the dryer for an increased process efficiency is limited and a possibility of outputting powder with high moisture content is likely in some conditions.